fix: use Object.is in replaceEqualDeep for correct NaN handling

[alex-js-ltd]

🎯 Changes

replaceEqualDeep previously used === for equality checks.

This causes an issue with NaN, since NaN === NaN is false. As a result, values containing NaN are treated as unequal, preventing structural sharing and causing unnecessary object replacement.

This PR replaces === with Object.is, which correctly treats:

• NaN as equal to NaN
• +0 and -0 as distinct

A test has been added to verify that objects containing NaN preserve reference equality.

✅ Checklist

• I have followed the steps in the Contributing guide.
• I have tested this code locally with pnpm run test:pr.

🚀 Release Impact

• This change affects published code, and I have generated a changeset.
• This change is docs/CI/dev-only (no release).

Summary by CodeRabbit

• Bug Fixes

  • Improved deep-equality logic so special numeric cases (notably NaN) are treated as equal, improving caching, comparisons, and reference preservation across nested structures.

• Tests

  • Added unit tests covering NaN in nested objects and arrays to ensure correct equality behavior and stable reference reuse.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: a9bfcb92-466a-4640-a1c5-3e3fb0480866

📥 Commits

Reviewing files that changed from the base of the PR and between 9a33a68 and d5fb45b.

📒 Files selected for processing (1)

• packages/query-core/src/__tests__/utils.test.tsx

🚧 Files skipped from review as they are similar to previous changes (1)

• packages/query-core/src/tests/utils.test.tsx

---

📝 Walkthrough

Walkthrough

Replaced === with Object.is in replaceEqualDeep to treat NaN as equal; added unit tests for NaN-related cases and a changeset documenting a patch release for @tanstack/query-core.

Changes

Cohort / File(s)	Summary
Changeset Documentation .changeset/happy-banks-repeat.md	Adds a changeset entry declaring a patch release for @tanstack/query-core describing the replaceEqualDeep fix.
Core Implementation packages/query-core/src/utils.ts	Replaces === with Object.is in replaceEqualDeep for top-level and recursive comparisons, altering equality semantics for NaN and signed zero.
Test Suite packages/query-core/src/__tests__/utils.test.tsx	Adds tests asserting reference preservation and NaN handling (including replaceEqualDeep(NaN, NaN) and nested/array cases).

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 I nibble code beneath the moonlit stand,

NaN finds itself a friend at hand.
Object.is hops in, switches the tune,
Deep trees stay cozy, same shapes in noon.
A tiny patch — a carrot for this land.

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely summarizes the main change: replacing === with Object.is in replaceEqualDeep specifically to fix NaN handling.
Description check	✅ Passed	The description follows the template structure with all required sections completed: Changes section explains the problem and solution, Checklist confirms testing and contributing guide compliance, and Release Impact confirms changeset generation.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

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[coderabbitai]

🧹 Nitpick comments (1)

packages/query-core/src/__tests__/utils.test.tsx (1)

419-424: Good test coverage for the NaN fix.

The test correctly validates that structural sharing works when objects contain NaN values.

For completeness, consider adding tests for:

• Top-level primitives: expect(replaceEqualDeep(NaN, NaN)).toBe(NaN)
• Arrays containing NaN: expect(replaceEqualDeep([NaN], [NaN])).toBe(prev)

🧪 Additional test cases

     it('should return the previous object reference when values contain NaN', () => {
       const prev = { value: NaN }
       const next = { value: NaN }
       expect(replaceEqualDeep(prev, next)).toBe(prev)
     })
+
+    it('should return the previous value when both values are NaN', () => {
+      expect(Number.isNaN(replaceEqualDeep(NaN, NaN))).toBe(true)
+    })
+
+    it('should return the previous array reference when values contain NaN', () => {
+      const prev = [NaN, { a: 1 }]
+      const next = [NaN, { a: 1 }]
+      expect(replaceEqualDeep(prev, next)).toBe(prev)
+    })

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@packages/query-core/src/__tests__/utils.test.tsx` around lines 419 - 424, Add
two more tests for replaceEqualDeep: one that verifies top-level primitives with
NaN return the same primitive (use expect(replaceEqualDeep(NaN,
NaN)).toBe(NaN)), and one that verifies arrays with NaN preserve structural
sharing (create const prev = [NaN]; const next = [NaN];
expect(replaceEqualDeep(prev, next)).toBe(prev)). Ensure both tests live
alongside the existing NaN test and reference the replaceEqualDeep function.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@packages/query-core/src/__tests__/utils.test.tsx`:
- Around line 419-424: Add two more tests for replaceEqualDeep: one that
verifies top-level primitives with NaN return the same primitive (use
expect(replaceEqualDeep(NaN, NaN)).toBe(NaN)), and one that verifies arrays with
NaN preserve structural sharing (create const prev = [NaN]; const next = [NaN];
expect(replaceEqualDeep(prev, next)).toBe(prev)). Ensure both tests live
alongside the existing NaN test and reference the replaceEqualDeep function.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 35d095f1-e907-44e9-90e4-f2bd81f742ab

📥 Commits

Reviewing files that changed from the base of the PR and between 1047cdc and 9a33a68.

📒 Files selected for processing (3)

• .changeset/happy-banks-repeat.md
• packages/query-core/src/__tests__/utils.test.tsx
• packages/query-core/src/utils.ts